Date: Sun, 2 Jul 1995 12:34:56 +0400 (MSD) From: =?KOI8-R?Q?=E1=CE=C4=D2=C5=CA_=FE=C5=D2=CE=CF=D7?= aka "Andrey A. Chernov, Black Mage" <ache@astral.msk.su> To: CVS-commiters@freefall.cdrom.com, Bruce Evans <bde@zeta.org.au>, cvs-sys@freefall.cdrom.com Subject: Re: cvs commit: src/sys/i386/isa sio.c Message-ID: <YbmebzlqJH@astral.msk.su> In-Reply-To: <199506300206.MAA21212@godzilla.zeta.org.au>; from Bruce Evans at Fri, 30 Jun 1995 12:06:11 %2B1000 References: <199506300206.MAA21212@godzilla.zeta.org.au>
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In message <199506300206.MAA21212@godzilla.zeta.org.au> Bruce Evans
writes:
>> Modified: sys/i386/isa sio.c
>> Log:
>> Fight with hanging modems continued:
>> return EIO after t_timeout expired instead infinite looping in "siotx"
>> in comparam, consuming CPU time.
>Why does this loop occur? It can't happen with working 8250..16550
>chips? It might happen if the UART incompatibly implements ctsflow
>in hardware. Otherwise, hangs here are quite different from the
>ctsflow-related hangs solved elsewhere using t_timeout.
Bruce, I don't know, *why* it occurs, I am not hardware expert.
I only know that it *occurs* sometimes and my goal is to make
modem pool which can work without human eye when possible.
This thing cures by dropping DTR, EIO here usualy cause close
and DTR drop. I am not think, that it is CTS hang, symptom
are: modem TX light is on forever (sio waits, when TX done
forever too). Joerg f.e. send me "thanx" for this fix, he
have this situation too (it means that it isn't only my hardware).
After few years of dealing with modem pools I know,
that *all* hardware are broken and good hardware simple doesn't
exists. It means, that sio/tty driver must *not* have infinite
loops and have reasonable timeout for each potential long-time
operation. I understand, that even now not all such places
handled with timeouts, but I prefer to fix only *real* bugs,
not potential ones.
--
Andrey A. Chernov : And I rest so composedly, /Now, in my bed,
ache@astral.msk.su : That any beholder /Might fancy me dead -
FidoNet: 2:5020/230.3 : Might start at beholding me, /Thinking me dead.
RELCOM Team,FreeBSD Team : E.A.Poe From "For Annie" 1849
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